Method and control device for open-loop or closed-loop control of a vehicle brake system

Abstract

A method for carrying out closed-loop or open-loop control of a vehicle brake system includes, when a braking request signal is present, setting brake pressures at brakes on axles and/or wheels of the vehicle by distributing brake pressure. Before braking is initiated on the basis of current, received or detected data relating to friction conditions or grip conditions between the roadway surface and tire surfaces of the vehicle, a determination is made as to whether, or to what extent, the distribution of brake pressure occurs in a brake wear pressure distribution or in a frictional engagement pressure distribution for the subsequent initiation of the braking process.

What is claimed is: 
     
       1. A method for controlling a brake system of a vehicle, the method comprising determining when a braking request signal is present; when a braking request signal is present and before initiating braking, using at least one data processor associated with the vehicle to determine, based on a comparison of a threshold coefficient of friction with data concerning frictional conditions between a roadway surface and tire surfaces of the vehicle, to what extent brake pressure is to be distributed to brakes of the vehicle by at least one of brake wear-pressure distribution and grip-pressure distribution; and outputting control signals for setting brake pressures for at least one wheel of the vehicle. 
     
     
       2. The method as claimed in  claim 1 , wherein the data concerning frictional conditions comprises at least one of roadway measurement signals of a roadway detector configured to detect a surface of the roadway and weather measurement signals of at least one of a temperature detector configured to detect an ambient temperature, a rain detector, and a vehicle surroundings detection system including a camera for detecting fog, snow and rain. 
     
     
       3. A method for controlling a vehicle brake system, comprising, when a braking request signal is present, before initiating braking, using at least one data processor to determine, based on data concerning frictional conditions between a roadway surface and tire surfaces of the vehicle, to what extent brake pressure is to be distributed to brakes of the vehicle by at least one of brake wear-pressure distribution and grip-pressure distribution; and outputting control signals for setting brake pressures for at least one wheel of the vehicle, wherein the data concerning frictional conditions comprises navigation data comprising map data and global position data including data concerning at least one of roadway gradients, roadway bends, roadway status, and traffic patterns of a route section in a path of the vehicle. 
     
     
       4. The method as claimed in  claim 1 , wherein the data concerning frictional conditions comprises data relating to a status of the tire surfaces. 
     
     
       5. A method for controlling a vehicle brake system, comprising, when a braking request signal is present, before initiating braking, using at least one data processor to determine, based on data concerning frictional conditions between a roadway surface and tire surfaces of the vehicle, to what extent brake pressure is to be distributed to brakes of the vehicle by at least one of brake wear-pressure distribution and grip-pressure distribution, by comparing a currently determined coefficient of friction against at least one threshold, and, when the coefficient of friction is less than a first threshold, setting the grip-pressure distribution, and, when the coefficient of friction exceeds one of the first threshold and a further threshold, setting the brake wear-pressure distribution. 
     
     
       6. The method as claimed in  claim 5 , wherein the at least one threshold is a function of a route in a path of the vehicle. 
     
     
       7. A method for controlling a vehicle brake system, comprising, when a braking request signal is present, before initiating braking, using at least one data processor to determine, based on data concerning frictional conditions between a roadway surface and tire surfaces of the vehicle, to what extent brake pressure is to be distributed to brakes of the vehicle by at least one of brake wear-pressure distribution and grip-pressure distribution, wherein, compared to brake lining wear-pressure distribution, in grip-pressure distribution, a higher brake pressure is applied to the brakes of an axle of the vehicle to which a relatively high axle load is applied, and a lower brake pressure is applied to the brakes of an axle of the vehicle to which a relatively light axle load is applied. 
     
     
       8. A method for controlling a vehicle brake system, comprising, when a braking request signal is present, before initiating braking, using at least one data processor to determine, based on data concerning frictional conditions between a roadway surface and tire surfaces of the vehicle, to what extent brake pressure is to be distributed to brakes of the vehicle by at least one of brake wear-pressure distribution and grip-pressure distribution; and outputting control signals for setting brake pressures for at least one wheel of the vehicle, the determination including determining brake pressure distribution between at least one of axles and wheels of the vehicle by determining a pure grip-pressure distribution and a pure brake lining wear-pressure distribution and subsequent formation of mean values from the pure grip-pressure and pure brake lining wear-pressure distributions for at least central grip ranges. 
     
     
       9. The method as claimed in  claim 8 , wherein the mean values are formed by one of a linear function, a step function and a non-linear, continuously differentiable function. 
     
     
       10. A method for controlling a vehicle brake system, comprising, when a braking request signal is present, before initiating braking, using at least one data processor to determine, based on data concerning frictional conditions between a roadway surface and tire surfaces of the vehicle, to what extent brake pressure is to be distributed to brakes of the vehicle by at least one of brake wear-pressure distribution and grip-pressure distribution; before initiating braking as a function of the frictional conditions, classifying into more than two classes different proportions of grip-pressure distribution and brake wear-pressure distribution; and, in a class with a higher proportion of grip-pressure distribution and an axle to which a relatively high axle load is applied, setting a higher brake pressure than in a class with a relatively low proportion of grip-pressure distribution. 
     
     
       11. The method as claimed in  claim 10 , further comprising classifying ambient conditions into more than two classes, and, based thereon, changing a proportion of brake pressure acting on the brakes of the axle to which a heavy axle load is applied. 
     
     
       12. A control device for a vehicle brake system configured to effect the method as claimed in  claim 1 , the control device being configured to receive the braking request signal and determine a distribution of brake pressure. 
     
     
       13. A brake system for a vehicle, comprising the control device as claimed in  claim 12 ; brakes at wheels of a front axle and wheels of a rear axle of the vehicle; wheel speed sensors for measuring wheel speeds; and valves for modulating brake pressure in the brakes; wherein the control device is configured to receive the braking request signal from at least one of a brake value signal transmitter and a vehicle dynamics control device, determine brake activation operations at the brakes based on the braking request signal, and output brake control signals to the valves. 
     
     
       14. A vehicle, comprising the brake system as claimed in  claim 13 . 
     
     
       15. A method for controlling a vehicle brake system, comprising, when a braking request signal is present, before initiating braking, using at least one data processor to determine, based on data concerning frictional conditions between a roadway surface and tire surfaces of the vehicle, to what extent brake pressure is to be distributed to brakes of the vehicle by at least one of brake wear-pressure distribution and grip-pressure distribution; and outputting control signals for setting brake pressures for at least one wheel of the vehicle, wherein the data concerning frictional conditions comprises data relating to at least one of brake lining wear, previous distance traveled, and previous braking performance of wheels of the vehicle.